“…Therefore, monitoring the aging status of the transformer will be helpful to prevent system failure (Lin, Wu, & Chung, 2008). Since digital PD detection is developed (Ward, 1992) has extremely high diagnosis accuracy for insulating medium (James & Phung, 1995;Tanaka, 1995), it is an efficient way to well identify the aging status of cast-resin transformer for maintenance or replacement to further prevent insulation breakdown (Farag et al, 1999;James & Phung, 1995;Karthikeyan, Gopal, & Venkatesh, 2008;Tanaka, 1995;Yue, Chen, Cheng, Song, & Xie, 2006).…”